Applet is not working in browser

I have created a Java applet in Eclipse and ran it in eclipse, it works fine . To run the applet in Webbrowser it was mentioned to embed the .class file inside a webpage by creating a HTML file. My class name is MyFirstGUI. i have created a file name gui.html and saved it in my documents. The error im getting in browser when running the file is "ClassNotFoundException". This is the content of my html file .

Make sure the class file is located in the same directory as the html file. also make sure it is actually an applet rather than an aplication (has an init and a paintComponent method and it extends JApplet).

i have created it in NetBeans sorry not in Eclipse as i mentioned, so it is saved inside netbeans projects folder, i have also cpoied the HTMl file to the same location which is " C:\Users\jacksons5\Documents\NetBeansProjects\myFirstGUI\build\classes\myfirstgui " . Its still throwing the same error.